Jaw motion is classified into rotating motion of the mandibular condyle with the mandibular fossa as a bearing, and gliding motion in which the mandibular condyle moves forward. For example, when the mouth or jaws are opened/closed slightly due to chewing or the like, mainly rotating motion arises. On the other hand, when the mouth or jaws are greatly opened/closed by yawning or the like, not only rotating motion, but gliding motion also arises. Abnormalities of the jaw oral cavity functions, such as mismatching of the occlusion or the like, can be diagnosed from measurements of these jaw motions. In order to carry out appropriate treatment, it is important to accurately measure jaw motion for each subject.
Current, there exist “GNATHO-HEXA” and the like, which is manufactured by GC Corporation, as jaw motion measuring devices that are becoming popular among some clinicians. Refer to www.gcdental.co.jp/product/pdf/nasohekisa.pdf on the Internet. This device attaches, to the patient, a headgear, and an implement that fixes to the row of teeth, and measures three-dimensional motions such as chewing motion, opening/closing motion, and the like. Namely, the relative position of the lower jaw is measured, and jaw motion measurement is carried out. In addition thereto, for example, devices called “kinesiographs” are becoming popular. This is a device that fixes a magnet to the row of teeth of the lower jaw, and three-dimensionally measures jaw motion by capturing magnetism. These two are representative as devices that measure jaw motion in current clinic settings.
Further, in Japanese Patent Application Laid-Open No. 2008-18094 (JP200818094A1) and Japanese Patent Application Laid-Open No. 2008-18010 (JP200818010A1), there are proposed, as techniques that easily carry out jaw motion measurement, various techniques of attaching an acceleration sensor to the chin portion or the like of the lower jaw, and measuring the oral cavity motion of a subject on the basis of the output of the acceleration sensor.